Icfa Instrumentation Bulletin* Fall 2002 Issue Icfa Instrumentation Bulletin Table of Contents Design and Quality Assurance Stations " 1 G. D. Hallewell, " Technology Developments for Deep Underwater Neutrino Telescopes " 17

The hadronic calorimeter for the CMS experiment requires photodetection in a 4 Tesla magnetic field. This, plus high neutron radiation and a 25 ns bunch-crossing, necessitated the development of a new type of high-rate multi-channel hybrid photodiode. As our specifications became tighter, design changes in the diode structure and surface treatment became necessary, resulting in a better product with very low crosstalk in both AC and DC modes. The specifications are rigorous and are maintained by a set of automated Quality Assurance stations which will process 570 tubes over 2 years.